The present invention relates to a pneumatic tire having a single carcass reinforced with high strength metallic cords and a high ending turnup and a locked bead construction.
The desirability of having the turnup portions of the carcass ply (or plies) of a pneumatic tire extend radially outwardly of the bead core the shortest possible distance is the premise on which prior art locked beads were developed. The proposed advantages included improved bead durability, and reduced material costs.
U.S. Pat. No. 4,922,985, issued May 8, 1990, discloses a carcass ply 30 having a main portion that extends between both bead cores (not shown) of the tire and turnup portions that are anchored around each bead core 31. Tires according to U.S. Pat. No. 4,922,985 have the radially outer edges of the turnup portions of the carcass ply disposed radially outwardly of the bead cores a minimal distance and are in contact with the main portion of the carcass ply. Suitable elastomeric materials surround the bead core, carcass ply and other elastomeric components to complete the bead portion of the tire. In FIG. 4 of this patent, there is illustrated a clamping member 432 comprised a strip of side-by-side cords of a heat shrinkable material embedded in a suitable elastomeric substance having a permanent thermal shrinkage of at least 2 percent. This strip of cords extended from a location radially and axially inward of the bead core 431 to a location radially outward of the bead core and there was no filler strip or apex disposed between the main portion and turnup portion of the carcass ply.
Tires according to U.S. Pat. No. 4,922,985 were manufactured using a clamping member in which the heat shrinkable material was 1260/2 Nylon 6,6, having a permanent thermal shrinkage of about 4 percent. It is continually the goal in the art to simplify the construction and reduce the expense of building tires, yet improve the durability, handling, rolling resistance and other properties of tires.
The present invention relates to a pneumatic tire having a pair of axially spaced apart annular bead cores and a single carcass ply which is folded about each bead core. Each bead core comprises a plurality of wraps of a single metallic filament. The single carcass ply is reinforced with parallel metallic cords composed of at least one filament having a tensile strength of at least (xe2x88x922000xc3x97D+4400 MPa)xc3x9795%, where D is the filament diameter in millimeters. The single carcass ply is folded about each bead core. The single carcass ply has a main portion that extends between the bead cores and turnup portions that are folded around the bead cores. A radially outer edge of each turnup portion is in contact with the main portion of the carcass ply and extends to an end point 0.5 inches (12.7 mm) to 4.0 inches (101.6 mm) radially outward of the bead core, as measured along the main portion of the carcass ply of the tire. No bead apex or filler is present between the carcass turnup and the main portion of the carcass ply. A toe guard associated with each bead has each end (first and second) of the toe guard being disposed directly adjacent to the carcass ply. One (the first) end is located on the axially inner side of the main portion of the carcass ply at a location about 0.4 to 3.5 inch(s) (10 mm to 89 mm) radially outward of the bead core as measured along the main portion of the carcass ply. The other or second end of the toe guard is located at a point ranging from substantially the axially outermost point of the bead core to a location about 3.5 inches (89 mm) radially outward of the bead core as measured along the turnup portion of the carcass ply. The first end and second end of the toe guard is a shorter radial distance from said bead core than the end point of the turnup radial portion of the carcass ply. The respective turnup portion of the carcass ply is directly adjacent to both the toe guard and the bead core.